Tuesday, May 24, 2016

‘Biodegradable’ plastics are a big fat lie

 Sailing seas of plastic :
How much plastic is floating in our oceans ?

From HuffingtonPost by Chris d'Angelo

A prediction that the world’s oceans will contain more plastic than fish by 2050 is likely to intensify the push for sustainable, environmentally friendly alternatives.
Biodegradable plastics have long been touted as a “greener” technology, but a new report from the United Nations says these plastics do little, if anything, to actually protect the planet and marine creatures.
“Plastics marked as ‘biodegradable’ do not degrade rapidly in the ocean,” says the report, published Monday.

 Lemon shark is pictured with plastic bag caught around its gills in the Bahamas 
Jonathan Bird via Getty Images
The 179-page report on plastic marine debris is one of several documents released in time for the United Nations Environment Assembly, which kicked off Monday in Nairobi, Kenya.
Plastics, which can cause serious ecological harm, “are now ubiquitous in the ocean, found in every ocean and on every shoreline from the Arctic through the tropics to the Antarctic,” the report states.
Biodegradable plastics — which have been used for shopping bags, water bottles and food containers — are designed to be less durable and capable of degrading quickly in the environment. But the problem, according to the U.N., is that the conditions required for such plastics to break down exist almost exclusively in industrial composters, not in the ocean.
The description is “well-intentioned but wrong,” Jacqueline McGlade, chief scientist at the U.N. Environment Program, told The Guardian.
“A lot of plastics labelled biodegradable, like shopping bags, will only break down in temperatures of [122 degrees Fahrenheit] and that is not the ocean,” McGlade told the publication.
“They are also not buoyant, so they’re going to sink, so they’re not going to be exposed to UV and break down.”

 Plastic garbage is pictured on Eastern Island, in the Northwest Hawaiian Islands.
Roberta Olenick via Getty Images
The U.N. estimates that global plastic production grew 4 percent from 2013 to 2014, exceeding 311 million metric tons. At least 8 million metric tons — the equivalent of one garbage truck every minute — leak into the ocean each year, according to the World Economic Forum.
The U.N. says improving waste collection and management is the “most urgent solution” to reducing plastic litter, but social attitudes are also critical.
“There is a moral argument that we should not allow the ocean to become further polluted with plastic waste, and that marine littering should be considered a ‘common concern of humankind,’” the report says.
In other words, don’t pat yourself on the back the next time you reach for those biodegradable plastic bags.
We need to do a lot more than that.

Links :

Monday, May 23, 2016

How can modern satellites photos possibly be accurate to 20 centimeters in 10 kilometers?

3D WorldView-1 satellite view showing some of the ground survey points in PhotoSat’s Eritrea test area.

 From GIScafĂ© by Gerry Mitchell (Photosat)

My intuition rebels at the notion that a satellite orbiting 750 kilometers above the earth, traveling at 7 kilometers per second could possibly take photos of the ground accurate to 20 centimeters in 10 kilometers.
When I realize that these satellites have scanning cameras which take their photos like push brooms, with the north end of the photo taken a few milliseconds before or after the south end, and that the whole satellite is vibrating while the photos are taken, my mind boggles.
It just does not seem that such high accuracy should be possible.
The satellite photos themselves, checked with tens of thousands of ground survey points, clearly demonstrate that the accuracy is real.

How do the satellites and cameras work?

We engineers and geoscientists in the commercial realm don’t actually know how these satellites and cameras really work.
Almost all of the technical details of the imaging satellites, their cameras and their ground processing stations, are classified.
Or if they are not classified they are certainly very difficult to discover.
I have had many conversations with satellite engineers who seem like they would love to tell me why their satellites perform so amazingly well.
However, sadly, they are not allowed to.
They simply can’t discuss classified technology with anyone who doesn't have the appropriate security clearances.

Whenever I have one of these conversations it always seems to me that part of what the engineer knows is public and part is classified but the engineer cannot be sure that he or she can remember what is still classified and what isn’t.
Since the engineers don’t have perfect memories it is safest to say nothing.
I have had satellite engineers decline to confirm information that is published on their own company’s websites.
This can make for some very awkward conversations.
We engineers and geoscientists in the commercial world only have access to the satellite photos themselves and very general public information about the satellites and their cameras.

How accurate are the satellite photos?

When the Digital Globe WorldView-1 ( WV1) satellite photos first became commercially available in 2008, PhotoSat acquired stereo photos for a test area in and Eritrea where we had over 45,000 precisely surveyed ground points.
When we shifted the WV1 photos three meters horizontally to match any survey point we were amazed to discover that all of the survey points within 10 kilometers matched the satellite photos to within 20 centimeters.
We eventually documented this discovery in an accuracy study white paper that we presented at conferences and is now published on our web site.

Now, eight years after that initial WorldView-1 accuracy study of the Eritrea test area, we have processed hundreds of satellite photos from the WorldView, Pleiades, SPOT and KOMPSAT satellites and have come to expect this incredible accuracy.
I am still in awe that this is possible and I still don’t know how it is achieved.
I do know that the photos are amazingly accurate.

WorldView-1 satellite photo over the PhotoSat test area in Eritrea.
The over 15,000 ground survey points used to confirm that the satellite photo accuracy is better than 20 centimeters in 10 kilometers are shown as black dots.
The completely black areas are survey points every 20 meters along lines separated by 100 meters.

Colour image of a one meter PhotoSat survey grid produced from the WorldView-1 satellite photos.  The ground survey points demonstrate that the PhotoSat grid is accurate to 35 centimeters in elevation.

Sunday, May 22, 2016

Cavitation explained

Cavitation is the formation of vapour cavities in a liquid – i.e. small liquid-free zones ("bubbles" or "voids") – that are the consequence of forces acting upon the liquid. 
t usually occurs when a liquid is subjected to rapid changes of pressure that cause the formation of cavities where the pressure is relatively low.
When subjected to higher pressure, the voids implode and can generate an intense shock wave.

Saturday, May 21, 2016

EgyptAir Flight MS804 crashed in deep seas near underwater mountains

Timeline of the crash

From NBCnews

Investigators searching for wreckage from EgyptAir Flight MS804 may face similar problems to those seeking the missing Malaysia Airlines jet — including tough terrain on the ocean floor and deep, heavy seas, experts said Friday.
Floating debris and personal belongings have been found in the Mediterranean Sea, Egypt's military said, but the hunt continues for the rest of the doomed plane including "black boxes" that could yield vital clues.
Key parts of the Airbus A320 have likely sunk to the seabed and could be hidden by ridges and underwater volcanoes as high as the Alps, according to Simon Boxall from Britain's National Oceanography Centre in Southampton, England.
"This is still a very inaccessible part of the planet," Boxall told NBC News, adding: "Oceans are very good at keeping their secrets."

 Hunt for EgyptAir flight 804 intensifies :
Even modest seas represent a big challenge for searching

While the Mediterranean is usually associated with sunshine and balmy waters, the sea where the jet is thought to have crashed — about 180 miles north of Alexandria, Egypt — is deep and often choppy.
"The depth in that area is in the region of 1.8 miles, which is significant and not much shallower than the area in the Indian Ocean where they are looking for [missing Malaysia Airlines flight] MH370," Boxall said. "We are not talking shallow waters … this is well below what divers could reach."
Flight MS804, which was traveling from Paris to Cairo, disappeared from radar screens early Thursday with 66 people on board. Officials say it descended rapidly from cruising height, making a sharp left turn followed by a 360-degree turn to the right.

Area of the crash in the GeoGarage platform
290 km North of Alexandria (according Egyptian Army)

EgyptAir MS804 wreckage may be on one of the deepest parts of the Mediterranean.
(courtesy of MarineTraffic / video)

"Any substantial parts will likely by now be on the seabed which in this area is quite rocky with mountains and lots of ridges," Boxall said.
"It is not a simple area in which to search and recover things from the seabed. The assumption is that the Med is sunny and calm but I've worked in that area and when it gets rough, it gets very rough."
The faster debris can be recovered from the water, the more experts will be able to discover about what happened to the plane, former NTSB air accident investigator Greg Feith told NBC's TODAY.
"As long as it doesn't get washed ... as long as the exposed parts aren't continually being washed either by wave or tidal action or any kind of grit or sand on the bottom, there should be [explosive] residue ... that forensic folks can actually determine whether or not there was an explosion or ... some sort of deformation due to overload or some sort of breakup of the aircraft."

Swath bathymetry of East Mediterranean

International bathymetric chart of the Mediterranean (IBCM) :
thickness of the Plio-quatenary sediments (IBCM-PQ)

The difficulty of the task will also be determined by the speed and angle at which the jet entered the water.
"If the aircraft hit the sea directly then it will have broken up under the sheer force of impact, but if it was a low angle of approach there could be large sections relatively intact," U.K.-based consultant marine archaeologist Tim Akers said.
"Natural buoyancy could keep some of those parts afloat for a good few days."

 Sentinel-1A detects slick
The Sentinel-1A radar satellite detected a slick in the eastern Mediterranean Sea – in the same area that EgyptAir flight MS804 disappeared early morning of 19 May 2016 on its way from Paris to Cairo. Sentinel-1A acquired this image later in the day at 16:00 GMT (18:00 CEST) in ‘extra-wide swath mode’ of 400 km with horizontal polarisation.
ESA provided it to the relevant authorities to support the search operations.
The 2 km-long slick is located at 33°32' N / 29°13' E – about 40 km southeast of the last known location of the aircraft. Although there is no guarantee that the slick is from the missing airplane, this information could be helpful for the search.
(courtesy of ESA / closer view)

Despite the difficulties, the search for MS804 has several advantages compared to the fruitless two-year hunt for MH370.
Authorities quickly had clear picture of where there plane was last seen, compared to the case of MH370 in which it took days to piece together clues from satellite data.
"The search is much more limited — a small fraction of the area being covered in the Indian Ocean," Boxall said.
"Not only that, but it is in a busy shipping area and is within the flying range of helicopters. The MH370 search area was three days away from the nearest ship and search planes had to turn back for fuel after only a couple of hours."
The Mediterranean Sea is also heavily mapped — in contrast to the uncharted southern Indian Ocean where MH370 searchers had to spend weeks building up a profile of underwater mountains and other potential hazards before sonar searching could begin.

The speedier search also increases the chances that experts can identify the battery-powered "ping" signal from the aircraft's bright orange cockpit voice recorder and flight data recorder.
"The black boxes will still be 'pinging' if they haven't been damaged and it should still be a clear signal," Boxall said.
"It would seem to be a case of 'when' the wreckage is found, rather than 'if.'"

Friday, May 20, 2016

NZ Linz update in the GeoGarage platform

6 nautical raster charts updated

Exploring the far-flung natural beauty of the Bahamas’ ‘out’ islands

Bahamas islands with the GeoGarage platform

From The Washington Post by Scott Elder

“Make sure you hold onto something,” I say with mock seriousness to Elena as she takes her seat at the bow.
“If we run aground, we could fly into the water.” She’s not a sailor — and frankly, I’m not much of one either — but she knows I’m kidding.
We’ve both volunteered for lookout duty on our just-rented catamaran.
We’re supposed to point out any hazards to the skipper.

 The author’s father, left, and brother sail across the Sea of Abaco.
(Scott Elder /for the Washington Post)

As we exit Marsh Harbour on Great Abaco Island in the Bahamas, I blithely take in the colorful scenery — until I catch an extremely clear (and perilously close) glimpse of the harbor floor.
I advise Elena to follow me farther back on the boat and to grab a handrail, this time not joking at all.
We skirt over the shallows by about a foot and a half (the captain, my father, was anxiously watching the depth gauge) and enter the reassuringly wide open Sea of Abaco.
But even in the middle of this “sea,” about a mile from the nearest shore, the depth reading stubbornly hovers around 12.5 feet. Under a high sun, the water glows a gorgeous aquamarine.
To sailors, that blue-green means shallow water, and shallow water means danger.
Our knowledge of the Bahamian Abaco Islands was as shallow as their waters when my father; his girlfriend, Elena; my brother Mark; and I chose them as the destination for a week-long sailing trip.

On a map (but not a nautical chart), the Abacos look like the sailing equivalent of a bunny slope.
The main island, Great Abaco, and its neighboring arc of cays are separated by only a few miles, short hops compared with the long inter-island crossings we’d made during our previous three bareboat (that is, without a hired captain or crew) charters in the Caribbean.

The only time I’d visited the Bahamas before was a quick getaway to touristy Nassau, so I was eager to explore the natural beauty and culture of some far-flung Bahamian “out islands.” I also figured the quick and easy pinballing between harbors would leave me plenty of time to check two Bahamian attractions off my bucket list: swimming in a submerged sinkhole called a “blue hole” and eating conch I dove for myself.
However, during our pre-sail briefing, when the charter company staffer started talking about the tide — a nonissue in lower latitudes — and something called a “rage sea,” we realized we were in for some actual sailing.
Instead of carefree pinball bounces, our first two entrances into harbors were more like precise and well-timed billiard shots.
On the first day, we had to hustle to Man-O-War Cay’s narrow, side-pocket inlet because both the tide and sun were going down.
Even after we secured the boat to a mooring ball, Dad looked as if his nerves had been cranked by a sailing winch.
The tension began to ease at our next stop, Hope Town on Elbow Cay.

 Looking down the stairs in Elbow Reef Lighthouse in Hope Town, Elbow Cay.
(Scott Elder /for the Washington Post)

We docked our boat in the reassuring shadow of the islet’s red-and-white lighthouse, then promptly dinghied toward the nearest beach.
Viewed from the sandy Atlantic shore, the turquoise water no longer caused worry, but beckoned.
We dove between miniature canyons of coral, watched a rainbow of parrot fish chomp away at the reef and happily cavorted in the light surf.
Conchs litter Elbow Cay, but unfortunately for my goal of personally harvesting some, the ones I saw were on land, decorating the fringes of people’s yards in charming, tidy rows.
Our walk past Hope Town’s cheery pastel homes led us to Cap’n Jack’s, a harborside bar/restaurant with a dock/patio out back.
When I overheard a server’s strong New England accent, I asked him about his experiences as an expat in the Abacos.
“I’m actually from Nassau,” he politely explained.
“But people always guess Boston or New Hampshire.” I later learned that many northern Loyalists and freed blacks fled to the Bahamas after the Revolutionary War, settling in Nassau and, in particular, the Abacos.
(When the Bahamas also moved toward independence in the 1970s, a majority of Abaconians petitioned the British government to retain the area, without success.)

 Abacos with the GeoGarage platform

The settlers hoped to start farms on the Abacos, but that didn’t pan out because of the thin, sandy soil.
In the 19th century, a curious local industry emerged that took advantage of an abundant natural resource: dangers to boats.
“Wrecking,” or the salvage of ships that crashed onto the Abacos’ 100-mile-long barrier reef, flourished until about 1870.
That was a few years after the candy-cane lighthouse near our boat was built under orders from London.
According to “Abaco: The History of an Out Island and Its Cays,” by Steve Dodge, locals sabotaged its construction, rightly worried that it would scuttle the business.
From the deck of our boat, we watched the light flash five times every 15 seconds, just as it has every night since an upgrade 80 years ago.
In the morning, we climbed its 101 stairs and checked out the impressive brass inner workings.
It’s powered like a giant grandfather clock — a keeper winds the weights every two hours.
We can attest that it’s a well-oiled machine: The cables and gears glistened in the sun, and a large bottle of 3-in-One Oil sat at the ready.
We were eager to power our boat in a similarly old-fashioned way.
We hadn’t caught the wind in our sails yet because our cautious navigation had obliged us to rely on the motors.
So we reentered the windy Sea of Abaco to find out whether we still knew the ropes, or “lines,” in proper sailing-speak.
We turned into the breeze, raised the main sail, eased out the boom’s line and then unfurled the forward sail, the genoa.
With a little cranking on the winch to trim our sails, we were moving at a respectable clip of eight knots.
“So we’re doing a broad run,” I said confidently, referring to our boat’s angle on the wind.
“No, son,” Dad sighed with exaggerated resignation.
“This is a broad reach.
Broad Run is a high school in Ashburn.”
Buoyed by our growing confidence that we could handle the waters, we ticked almost all of the planned destinations off our itinerary.
At Treasure Cay, we traipsed the three-mile picture-postcard crescent beach, and I took command of a hammock slung between two palm trees.
After finding placid swells in the Whale Cay Passage instead of much-dreaded rage seas, we merrily fed table scraps to the feral pigs of No Name Cay.
During our ramble across Green Turtle Cay by golf cart, we watched a firetruck-led parade come together in honor of the victorious youth football team.
And on Great Guana Cay, we joined the rollicking Sunday afternoon party at Nipper’s beachside bar.

 The view across Hope Town harbor.
The Elbow Reef Lighthouse is approximately 153 years old.
(Scott Elder /for the Washington Post)

 But not everything went smoothly.
A mild storm closed the Whale Cay Passage and set us back.
With only one more day until we had to return to base, the blue holes down south were out of reach.
That left just conch foraging on my personal to-do list.

We tied off in Hope Town Harbour, and then Mark and I tossed our snorkel gear in the dinghy and sped out along the shore.
In the water was plenty of life — a silver school of spade-like palometa, a couple skittish hawksbill turtles — but every conch I flipped was a pale empty shell.
Then Mark called out, “Hey, big conch here.”
I turned it over and saw bright orange, pink and, much to my relief, two freaky eyestalks.
On the way home, I spotted another big one in the seagrass and snagged it.
Back aboard, I quickly realized that finding the conch is the easy part.
I wasted half an hour hammering holes in the shells using a mini anchor, hoping to find the right spot to free the big resident snails.
(It looks really straightforward on YouTube, by the way.)
Either out of mercy or a desire to end the loud banging, a woman dinghied over from her boat and gave me some pointers.
(Pointer No.
1: “You keep pounding that conch against your boat, you’re going to lose your security deposit.”)
I finally removed and cleaned the white meat, Elena marinated it in lemon and garlic, and Dad fired up the grill.
I gave Mark a tasty-looking strip.
“Barf!” he declared before tossing it into the harbor.
He was right; it tasted about as bad as you’d expect a snail found on the bottom of the sea to taste.
But the check on the bucket list was sweet.

Links :

Thursday, May 19, 2016

Marine vessel tracking system also a lifesaver for wildlife

A gray whale. A new paper from WCS (Wildlife Conservation Society), in partnership with researchers and practitioners from National Oceanic and Atmospheric Administration, U.S. Coast Guard, Space Quest, Google, and SkyTruth, reviews the use of a maritime vessel communication and navigational safety system that is not only effective in protecting people, but wildlife such as whales, walruses, and other wildlife species as well.
With improvements, say the authors, the system will ultimately result in greater engagement by vessel companies and operators in the conservation of marine resources.
Credit: (c) Ricardo Antunes

From Phys.org

A new paper from WCS (Wildlife Conservation Society), in partnership with researchers and practitioners from National Oceanic and Atmospheric Administration, U.S. Coast Guard, Space Quest, Google, and SkyTruth, reviews the use of a maritime vessel communication and navigational safety system that is not only effective in protecting people, but wildlife such as whales, walruses, and other wildlife species as well.
With improvements, say the authors, the system will ultimately result in greater engagement by vessel companies and operators in the conservation of marine resources.

The Automatic Identification System—adopted by the International Maritime Organization in 2000 for use in collision avoidance, coastal surveillance, and traffic management— effectively accomplishes navigational safety goals, and provides pre-emptive maritime safety benefits.
The paper appears in a recent edition of Bulletin of Marine Science.
"AIS now provides a rich source of data to understand vessel traffic across the entire globe - even in the most remote areas of the open ocean," said Dr. Martin Robards, Director of WCS's Beringia Program.
"This system also has the potential to help us minimize the negative effects of shipping on wildlife."

"The AIS can become a vital tool in helping to protect whale and other marine mammal species, particularly in locations such as the Arctic where shipping is potentially on the increase," said Dr. Howard Rosenbaum, Director of WCS's Ocean Giants Program.
"AIS can be used to identify regions where shipping lanes and important marine mammal habitats and migrations overlap, as well as areas where ocean noise may be impacting acoustically sensitive species."

(A) Vessel density on the Dutch coast based on AIS data and attributes of vessel be- havior (reproduced from Willems et al. 2009 and used with permission).
Trajectories are for a week covering 160,000 km2.
The anchor zone and yielding ferry inserts are renderings of a day. 
(B) Vessel density of a stormy day: northwest wind with force 8 on the Beaufort scale change the movement patterns of vessels entering and leaving Rotterdam.
(C) Vessel density of areas where vessels sail <3 kt during calm weather can be overlaid on shipping lanes to show areas of potential risk.

Understanding vessel traffic in relation to marine conservation is critical, particularly given that maritime transport accounts for approximately 90 percent of all world trade.
The continued development of maritime transportation around the world, especially in new areas such as the Arctic, can increase conservation impacts to wildlife, including disturbance, fatal strikes, introduction of pathogens through ballast water, habitat destruction through anchoring (especially on corals), introduction of invasive species, air emis¬sions, noise, and fuel spills.
AIS works by continuously transmitting messages containing details such as vessel identification, position, heading and other data to networks of receivers that track the information.
Increasingly, satellites are involved in receiving this signals on little cube satellites.
While little bigger than a bread box, these receivers can process up to 4 million messages a day and track up to 130,000 vessels at one time.

Though not designed as a conservation tool, the system data enables users to understand, and subsequently to design tools that help mitigate the impacts of maritime traffic on the marine environment and wildlife.
AIS data have important applications in conservation science including describing baseline vessel use of a maritime area, assessing or modeling actual or potential environmental impacts, and monitoring environmental compliance.
The authors cite the example of using AIS to establish areas where large cetaceans and vessels are likely to over¬lap in space and time—a critical step to understanding and reducing vessel strikes.
Using tagged whales off the Panama Canal, researchers demonstrated significant overlap between whales and vessels, and offered a preferred shipping route and vessel speed recommendations—similar to the well known example of North Atlantic right whale vessel conflict avoidance at the entrance to Boston Harbor.

Figure 1. Top: Seasonality of bulk carrier vessel traffic in the Aleutian Archipelago, Bering, and Chukchi Seas. Summer (July) traffic sees less traffic in the central Aleutian arc and greater travel into the Chukchi Sea (primarily here to the Red Dog mine). 

Bottom: Seasonality (January and July) of fishing vessel activity in the Aleutian Archipelago, Bering, and Chukchi seas.

Also referenced is underwater noise that can cause adverse effects to marine organisms.
AIS provides a tool for helping understand underwater soundscapes and identifying sources of acoustic noises that can be linked to decreased fisheries catches or disruptions to marine mammal behaviors and migrations.
But, say the authors, AIS's full potential as a conservation tool is yet to be tapped.
The system could be greatly enhanced by modifications that allow for more consistent and reliable data.
"You would not believe how many spellings there are for any one destination or origin for a vessel," added Robards. "Dutch Harbor had to have over a dozen different renditions, exacerbating the complexities of assessing vessel routes."

In addition, standardizing data processing and making data archives available through an international repository would cut analysis costs and promote collaboration, but would require significant efforts to bridge the gap between private industry who are providing the system and federal or research efforts looking to provide value added benefits such as conservation.
The authors make specific recommendations for improving existing applications for conservation use including improving coverage and reliability and usability of data to a wider group of users and improvement and expanded users.
"Effectively conserving our vast oceans will require technological leaps and cross-sectoral collaboration. This important review articulates the potential promise of both in the use of big data from vessel tracking systems such as AIS as well as local applications for critical habitat and threatened species," said Dr. Caleb McClennen, Executive Director of WCS's Marine Conservation Program.
"As increased ship traffic begins to congest an increasingly ice free Arctic, the conservation sector must capitalize on tools such as these to protect its currently pristine seas."

Fortunately, there are some exciting examples of progress, in Alaska for example, a Cooperative Research and Development Agreement between the Marine Exchange of Alaska and the Coast Guard R&D Center is leading to the use of AIS transmitters to develop the Next Generation Arctic Navigational Safety Information System.
To date environmental information and virtual aids to navigation have been transmitted via several of the Alaska AIS network.

"Conservation science and policy applications of the marine vessel automatic identification system (AIS)—a review," appears in the online edition of the Bulletin of Marine Science. Authors include MD Robards of WCS, GK Silber and JD Adams of Office of Protected Resources - NOAA Fisheries, J Arroyo of U.S. Coast Guard, D Lorenzini of Space Quest, K Schwehr of Google, and J Amos of SkyTruth.